Cameras have long used turrets to switch mounted lenses. Turrets allow use of separate lenses in place of a zoom lens, at a savings of cost relative to a zoom lens of the same quality. On the other hand, turrets must move and precisely position each lens. This functionality is relatively easy to provide using costly mechanisms having close tolerances, but is more difficult using inexpensive mechanisms.
It is well known to use an over-center mechanism to switch a lens turret between positions. Such mechanisms have relatively powerful springs, which bias a turret toward the nearer of two positions. U.S. Pat. No. 6,449,430 to Tasaka et al., discloses a one-time-use camera, which has a switchable lens holder “kept respectively positioned exactly by the bias of” a toggle spring connected to the lens holder. The camera also has a retention spring that biases the lens holder toward a shutter cover.
Costs of inexpensive cameras can be reduced by allowing relatively large tolerances in most parts. A turret and connected over-center mechanism having such tolerances present a risk of tilting out-of-plane during switching between different lens positions. Such tilting can be caused by an inexact over-center biasing that tips the turret out-of-plane while urging the turret toward one or both lens positions. Countering the tilt by use of a strong retention spring runs the risk of stalling the turret.
Another risk of tilting can be presented by the use of a long lever to switch a lens turret. U.S. Pat. No. 4,690,531 uses a long lever to push against a turret having a connected over-center mechanism. The long lever allows for convenient positioning of a user control.
It would thus be desirable to provide camera assemblies and methods, in which the risk of lens turret tilting is reduced simply and inexpensively.